Door closers

ABSTRACT

A door closer comprises an actuator assembly ( 20 ) adapted for fitting within the thickness of a door and an anchor member ( 10 ) adapted for fitting in a door frame in opposed relation to said edge face of the door. An operating member ( 30 ) is driven by spring means ( 45 ) and coupled to said anchor member ( 10 ) to draw the door towards the door frame. An adjustable fluid-filled damper ( 50 ) is coupled to said operating member ( 30 ) and arranged to provide variable regulation the rate of movement of the operating member under the force of said spring means ( 45 ). Resilient thrust means ( 85 ) are arranged to exert an increased driving force of said operating member ( 30 ) and adjustable control means ( 100 ) are provided whereby said thrust means ( 85 ) is operative to augment the driving force to said operating member ( 30 ) over a defined but variable part of said range of movement corresponding to movement of the door over the final part of its movement into its closed position.

DESCRIPTION OF INVENTION

This invention concerns door closers of the kind comprising an actuatorassembly intended for concealed fitting within the thickness of a door,and an anchor member for fixing to a door frame, and in which anoperating member is coupled to said anchor member and is movable withinthe actuator assembly under the action of driving means, usuallycomprising one or more mechanical springs, and under the control of auni-directionally operative fluid-filled damper which serves to regulatethe rate of movement of the door in the direction of closure withoutsignificantly restricting the rate of movement of the door in thedirection of opening.

It is desirable for the action of any damper in such a door closer to beadjustable so as to enable the rate of closure to be set to fall withina chosen range despite variations in the weight and other parameters ofdifferent doors with which the closer may be used, and for the closer toprovide an augmented closing force as the door reaches its closedposition in order to overcome resistance from any latch fitted to thedoor.

GB 2 044 840 A discloses such a door closer, which comprises anactuating assembly which is disposed in a housing that is located withinthe thickness of the door, having an operating member which is movablelinearly by means of one or more coil springs, and coupled by a flexiblelinkage to the anchor member which is attached to the door frame.

EP 0 016 445 A discloses a door closer of this type in which adjustmentof the final part of the closure movement of the door is achieved bymeans of an adjustment member associated with the anchor member which isattached to the door frame, the adjustment member being disposed behinda mounting plate of the anchor member at a variable spacing so aseffectively to adjust the length of the coupling between the anchormember and the operating member in the actuator assembly. Thisarrangement does not make any provision for adjustment of the overallrate of closure, but only in the final closure position of the doorrelative to a final part of the travel of the piston in the door-closingdirection, in which final part of the travel the action of the damper isrendered ineffective so as to provide for a locally increased rate ofclosure movement to overcome any resistance which may be offered by adoor latch for example.

Although the rate of movement of the door as it approaches its positionof closure is increased, there is no provision for adjusting the drivingforce applied to the door over the final part of closure movement, asrelieving the effect of the damper does not increase the force appliedby the driving springs, but only allows the door to accelerate inresponse to the driving force and the closing action then relies on themomentum of the moving door to overcome latch resistance. However, theacceleration achieved depends on many variable factors, including theweight of the door, wind loading on the door, and frictional resistancein die hinges and in the latch itself etc., and accordingly such designsdo not entirely address the problem of overcoming resistance associatedwith a door latch.

DE 1 708 349 A discloses a door closer having a main spring which actsover the full range of movement of a rod which is coupled by a link toand anchor member, and a supplementary spring arranged end to end withthe main spring and effective to increase the driving force applied tothe rod over the final part of the closure stroke, but without provisionfor varying the point at which the supplementary spring becomeseffective.

Accordingly, it is an object of the present invention to make provisionfor an augmented closure force to come into play as the door approachesits position of closure, as compared with the force applied throughoutthe remainder of the range of movement, whilst providing for adjustmentof the operation to suit a wide range of requirements not achievedpreviously.

According to a first aspect of the invention we provide a door closercomprising in combination:

an anchor member for mounting on a door frame,

an actuator assembly for mounting within the thickness of a door whichis hinged for movement between open and closed positions relative tosaid door frame,

an operating member coupled by an articulated link to said anchor memberand mounted in said actuator assembly for a range of movement between aretracted position in which said anchor member is held immediatelyadjacent to said actuator assembly and an extended position in whichsaid anchor member is held in spaced relation to said actuator assembly,

resilient driving means arranged to exert a driving force on saidoperating member in a manner such as to drive said operating membertowards said retracted position and thereby draw said anchor member andsaid actuator assembly together such that, when installed, the doorcloser acts to draw the door into its closed position relative to theframe,

a damper connected to said operating member so as to control the rate ofmovement of the operating member in at least a direction towards saidretracted position, said damper comprising a cylinder containinghydraulic fluid, a piston rod carrying a piston which divides thecylinder into two chambers, and flow-restricting means to limit the rateof flow of hydraulic fluid flow one of said chambers to the other atleast in one direction of fluid flow in response to movement of saidoperating member towards said retracted position, an adjustable throttlewhich comprises two elements in combination, the flow restrictionimposed on the hydraulic fluid by said throttle being variable byrelative positional adjustment of said two throttle elements, and anadjustment member to enable one of said throttle elements to bepositionally adjusted relative to the other so as to vary the flowrestriction imposed on the hydraulic fluid by said throttle,

resilient thrust means arranged to exert an increased driving force onsaid operating member, and

control means whereby said thrust means is operative to apply saidincreased driving force to said operating member over a defined part ofsaid range of movement as said operating member approaches saidretracted position, corresponding to movement of the door over the finalpart of its movement into its closed position, and

an adjustment member operatively connected with said control means tovary the point in the range of movement of said operating member atwhich said resilient thrust means becomes operative to apply saidincreased driving force.

The control means preferably includes a detent means arranged to holdthe thrust means in a stressed condition over the whole of the range ofmovement of the operating means apart from said defined part thereof.

In one arrangement, the thrust means may include a compression springlocated within a guide member which is coupled to said operating meansand slidable therewith along a fixed shaft, and the detent means may bemounted on a carrier member which abuts one end of the compressionspring and is slidable on said fixed shaft and located on this saidguide member for limited movement longitudinally thereof, the detentmeans being engagable in an internal recess formed within said guidemember to hold the compression spring in a compressed condition, andbeing displaceable from said internal recess to release said compressionspring at a predetermined position along said shaft.

The detent means may be displaceable from said position of engagementwith said internal recess in said guide member into a position ofengagement with an external recess formed in said shaft to hold saidcarrier member in a predetermined position on said shaft. Preferably,the detent means comprises a plurality of balls located in one or moretransverse bores formed in the carrier member, and each of said balls isof a diameter greater than the radial spacing between said shaft andsaid guide member so that said balls are either held by said shaft insaid internal recess in said guide member or by said guide member insaid external recess in said shaft.

In a particularly preferred arrangement, the bores in which the ballsare located are formed with a radially inner portion having a diametersuch as to accept the ball with a slight clearance and a radially outerportion having a greater diameter, the two portions of the bore meetingat an internal shoulder which is located at a spacing from the shaftwhich is less than the radius of the ball. With this arrangement whenthe ball is held in the internal recess of the guide member, it has beenfound that the ball does not bind on the shaft, thereby allowing theshaft to move freely relative to the carrier.

In a preferred arrangement the cylinder of the damper is moveablerelative to the actuator assembly and the piston is static, and the flowrestriction means is incorporated into said piston and piston rod, andthe adjustment member has an operating element which is accessible fromone end of said piston rod.

The adjustment member may comprise a shaft located within an axial boreformed in said piston rod, with an external threaded formation engagingan internal threaded formation in the bore of the piston rod wherebyrotation of the shaft varies its axial position within said bore. Theshaft may be provided at one end with a needle formation which comprisesone of said throttle elements to cooperate with an orifice defined bythe other of said elements, and at its other end with a head formationwhereby the shaft may be rotated.

The thrust means may comprise one or more spring elements having ahigher rate than the resilient driving means. Preferably both thedriving means and the thrust means comprise one or more coiledcompression springs, but other arrangements are possible. For examplethe thrust means may comprise one or more stacks of Belville washers,and the driving means could comprise gas-springs.

In a particularly convenient arrangement, said thrust means and saiddriving means each comprise two elements disposed symmetrically relativeto a single damper means, but other arrangements are possible.

These and other features of the invention will now be described by wayof example with reference to the accompanying drawings wherein:

FIGS. 1A and 1B are partially sectioned side views of one embodiment ofdoor closer to which the invention is applied, comprising an anchorassembly and an actuator assembly, and shown with these assembliesrespectively in the “door closed” condition and in the “door open”condition;

FIG. 2 is a front end view of the actuator assembly in the direction ofarrow II of FIG. 1B,

FIG. 3 is a horizontal section on the line III—III of FIG. 1B,

FIG. 4 is a composite section substantially on the line IV—IV of FIGS.1A and 1B,

FIG. 5 is a longitudinal section through an adjustable damper assemblyincorporated in the closer.

FIG. 6 is a longitudinal section on the line VI—VI of FIG. 1B showingthe construction of thrust means in a first, compressed condition,

FIG. 7 is a longitudinal section on the line VII—VII of FIG. 1A showingthe construction of thrust means in a second, uncompressed condition,

FIG. 8 is a transverse section on an enlarged scale on the lineVIII—VIII of FIG. 6,

FIG. 9 is a section on the line IX—IX of FIG. 8,

FIG. 10 is a graph relating the closure force obtained from a closer inaccordance with the invention to the angle of opening, and

FIG. 11 is a graph relating the door closure speed to door closing time.

The door closer as illustrated in FIGS. 1 to 9 comprises an anchorassembly 10 which is adapted for mounting a door frame at a verticaledge thereof facing the hinged edge of a door hingedly carried by theframe, and an actuator assembly 20 which is adapted for mounting withinthe thickness of the door.

The anchor assembly 10 comprises a mounting plate 11 and an adjustmentplate 12 which is spaced from the mounting plate on the side thereofremote from the door by an adjustable distance. An adjusting screw 13 isengaged in a threaded hole 14 formed in the adjustment plate 12 and aslotted head portion 15 of the screw bears against the mounting plate 12and is accessible through a central hole 16 formed in the mounting plate11. It will be understood that by rotation of the screw 13 the spacingof the adjustment plate 12 and mounting plate 11 can be varied for thepurpose hereinafter described.

The mounting plate 11 is also formed with a pair of apertures 17 nearthe ends thereof and the adjustment plate 12 is formed with a pair ofapertures 18 aligned with the apertures 17 whereby the adjustment plate12 is coupled to an operating member 30 of the actuator assembly 20 ashereinafter described.

The actuator assembly 20 is so dimensioned as to be suitable for fittingwithin the thickness of the door and for this purpose is provided with amounting member 21 having bosses near the outer ends thereof formed withapertures 22 which align with the apertures 17 of the anchor assemblymounting plate 11, a central boss formed with a bore 23, andintermediate bosses formed with a respective bore 24 having a reduceddiameter portion intermediate the ends thereof, as shown clearly in FIG.1A.

The apertures 22 locate therein fixed sleeves 25 which are provided withan external flange 26 abutting against the end face of the boss aroundaperture 22. The central bore 23 is partially threaded to receive athreaded end portion of a rod 27, and the intermediate bores 24 eachlocate one end of a respective shaft 28 secured therein by means ofscrews as shown. The sleeves 25, rod 27 and shaft 28 extend parallel toone another and the ends of the shafts 28 furthest from the mountingmember 21 are supported by a transverse stop plate 29 which is securedto the free end of the rod 27 by means of a screw or the like.

The actuator assembly 20 further includes an operating member 30, asabove-mentioned, which is carried by the mounting member 21 and guidedfor longitudinal movement by the sleeves 25, rod 27 and shafts 28. Theoperating member 30 includes a pair of parallel shafts 31 which arelocated in the sleeves 25, and each has at one end a pivotal connection32 to a respective rigid link 33 which is disposed within the associatedsleeve 25 when the closer is in the “door closed” condition as shown inFIG. 1A. The links 33 have a pivotal connection 34 with respectiveheaded studs 19 which extend through the apertures 17 in the mountingplate 11 and through apertures 18 of the adjustment plate 12 of theanchor assembly 10. The links thus form an articulated connectionbetween the shafts 31 and the anchor assembly 10.

The operating member 30 further includes, at the other end of the shafts31, a cross-head 35 by which the shafts 31 are interconnected. Thecross-head 35 is formed with outermost bosses with apertures 36 throughwhich the shafts 31 extend and the cross-head is secured to the shafts31 by means of pins (not shown). As seen most clearly in FIGS. 5, 6 and7, the cross-head 35 is also formed with a central boss and a centralaperture 37 in which the end of the rod 27 is located with a sealingring, and a pair of intermediate bosses with apertures 38 through whichthe shafts 28 pass with clearance.

The operating member 30 is movable inwardly towards a retracted or “doorclosed” position as shown in FIG. 1A under the force of driving springs45, which, in the illustrated embodiment, compromise coil springsextending between the cross-head 35 and the flanges 26 on the fixedsleeves 25. In addition, floating sleeves 40 are located on each of theshafts 31 and carry a respective clip 41 which engages between turns ofthe respective spring 45. Alternatively, separate springs may beprovided on opposite sides of the clip 41.

As will be evident, the compression springs 45 act on the cross-head 35to drive the latter inwardly of the actuator assembly 20 to theretracted position and to draw the shafts 31 and the associated links 33inwardly so as to bring the mounting plate 11 of the anchor assembly 10up to the mounting member 21 of the actuator assembly, in the mannerillustrated in FIG. 1A, thereby holding the door in its closed position.

When the door is opened, as shown in FIGS. 1B and 3, the shafts 31 andcross-head 35 are drawn outwardly, thereby causing the springs 45 to becompressed, abutment of the floating sleeves 40 against the fixedsleeves 25 limiting the outward travel of the cross-head 35 at anextended or “door open” position. When the door is released, the coilsprings 45 act to return the cross-head 35 and the shafts 31 to theirstarting positions, thereby bringing the door back to its closedposition relative to the frame.

The actuator assembly 20 further includes a damper assembly 50 toregulate the rate of closure of the door under the action of the springs45.

The damper assembly 50 as shown in FIG. 5 comprises a fixed piston 51formed on the rod 27 at an intermediate position, and a cylinder 52carried by the cross-head 35 and containing hydraulic fluid. Thecylinder 52 is located at one end, with an appropriate seal, in a recess53 formed in a boss at the centre of the cross-head 35, and is closed atits other end by a plug 54, which is retained by means of a clip 55 inthe mouth of the cylinder. The plug 54 is formed with a bore 56 throughwhich the piston rod 27 passes. Appropriate sealing rings 57, 58 arearranged to engage sealingly with the exterior surface of the rod 27 andwith the interior surface of the cylinder 52 as shown.

In the illustrated embodiment the fixed piston rod 27 is assembled fromfirst and second rod sections 59, 60. The first rod section 59 is formedwith a radial enlargement having a peripheral groove 61 for a sealingring 62 which engages with the interior face of the cylinder 52 so thatthe enlargement serves as the piston 51. The second rod section 60includes a widened end portion 63 which has in internal bore 64 toreceive an end portion of the first rod section 59.

The piston 51 divides the cylinder 52 into inner and outer compartments65, 66 and fluid passageways as hereinafter described are formed in thepiston 51 and the rod 27 to enable hydraulic fluid to pass from onecompartment of the cylinder to the other in a controlled manner.

Axial passageways 67 extend directly between opposite faces of thepiston 51. The widened end portion 63 of the second rod section 60 hasan end face 68 which is spaced axially from the piston 51, and aflexible seal 69 is disposed between the end face 68 and the piston 51.The flexible seal 69 is moveable within the gap between the end face 68and the piston 51 in response to fluid pressure so to close or open theaxial passageways 67.

The flexible seal 69 lifts from the ends of the axial passageways 67 inresponse to opening movement of the door, so that fluid may flow freelyfrom the inner compartment 65 to the outer compartment 66 and the doormay be opened freely. However, in response to movement of the doortowards its closed position the flexible seal 69 covers the ends of theaxial passageways 67 in such a manner as to prevent liquid flowingdirectly from the outer compartment 66 to the inner compartment 65through the axial passageways 67.

To enable fluid to flow from the outer compartment 66 to the innercompartment 65, radial passageways 70 are formed in the first rodsection 59 adjacent to the face of the piston which is presented towardsthe cross-head 35 to communicate with a central bore 71 whichterminates, at the end of the first rod section 59 which is presentedtowards the mounting member 21, in a throttling orifice 72. Furtherradial passageways 73 extend from the outer face of the widened endportion 63 of the outer rod portion 60 to a central chamber 74 formed atthe inner end of an axial bore 75 which extends through the second rodsection 60 to its outer end where it is received in the central bore 23of the mounting member 21.

The axial bore 75 includes a widened end portion 76 adjacent to thecentral chamber 74, and an internally threaded portion 77 adjacent tothe widened end portion 76. The widened end portion 76 receives anadjustable throttle member 80 which includes an externally threadedshank portion 81 received within the internally threaded portion 77 ofthe bore 75, and a needle port ion 82 which co-operates with the orifice72. The shank portion 81 of the throttle member 80 is formed with slot83 to receive the end of a screwdriver blade which can be inserted alongthe bore 75, to enable the throttle member 80 to be rotated to adjustthe axial position of the needle portion 82 relative to the throttleorifice 72 to provide a variable restriction.

When the passageways 67 are closed by the flexible seal 69,communication between the two compartments of the cylinder 52 is onlypossible through passageways 70, 71 and 73, and the throttling orifice72. In this way, the orifice 72 serves as an adjustable throttle toregulate the flow of fluid from the outer compartment 66 to the innercompartment 65 as the cross-head 35 is driven inwardly of the actuatorassembly by the compression springs 45. The rate at which the door isclosed under the force of the springs 45 can thus be adjusted, and it isparticularly to be noted that such regulation is effective throughoutthe entire range of movement of the operating member 30 from theextended position shown in FIG. 1B to the retracted position shown inFIG. 1A. However, on the reverse stroke, when the door is being opened,the flexible seal 69 is able to lift from the ends of the axialpassageways 67 and allow relatively unrestricted flow of fluid betweenthe two compartments.

The actuator assembly 20 further includes a pair of thrust assemblies 85mounted on the shafts 28 disposed between the respective driving springs45 and the damper assembly 50.

As can best be seen from FIGS. 6 and 7 an innermost end portion 86 ofeach shaft 28 is of slightly greater diameter than the outermost endportion 87 so as to form an outwardly facing shoulder 88 at the junctionbetween the two portions. A groove 89 is formed around the narrowerportion 87 of each shaft 28 at a predetermined spacing from the shoulder88.

The thrust assemblies 85 each include a thrust spring 90 located on therespective shaft 28 and within a cylinder 91 concentric with the shaft.Each cylinder 91 is fixed in a recess 92 formed in the intermediate bossof the cross-head 35, and serves as a guide for the thrust spring 90.The thrust springs 90 are strong compression springs having a rategreater than that of the coil springs 45.

An internally widened end portion 93 of each cylinder 91 forms anoutwardly facing shoulder 94, and internally the widened end portion 93is formed with a circumferential groove 95 at a predetermined spacingfrom the shoulder 94. The arrangement is such that when the cross-head35 abuts the stop plate 29 as shown in FIG. 7, the groove 95 in thecylinder 91 is longitudinally offset relative to the groove 89 formed inthe shaft 28, so as to be somewhat further from the mounting member 21.The widened end portion 93 of each cylinder 90 is fitted with aretaining clip 96.

A control mechanism 100 is provided whereby said thrust springs 90 areemployed to augment the force of the driving springs 45. The controlmechanism includes in each cylinder 91 a carrier block 101 which is heldin contact with the retaining clip 96 by engagement with the thrustspring 90. As best seen in FIGS. 8 and 9, the carrier block 101 isformed with a central bore 102 whereby it is slidable on the narrowerportion 87 of the shaft 28. The carrier block 101 is also formed withtwo intersecting transverse bores 103, 104 which contain four balls 105in the respective radial arms thereof. The transverse bores 103, 104,balls 105 and grooves 89 and 95 are so dimensioned that the balls 105may be displaced radially to seat in either the groove 89 formed on theshaft 28, or in the groove 95 formed in the cylinder 91.

As can be seen from FIG. 7, when the door closer is in its closedcondition the balls 105 are located in the groove 89 formed in the shaft28, and they are held in this position by engagement of the balls 105with the interior surface of the widened end portion 93 of theassociated cylinder 91 at a point spaced outwardly from the groove 95 bya small distance. The balls thus act as a detent means which holds thecarrier block 101 in a pre-determined position on the shaft 28, in whichposition the carrier block is spaced from the shoulder 94 in thecylinder 91 and the thrust spring 90 is in a relatively extendedcondition.

As the door is opened, the cross-head 35 and cylinders 91 move outwardly(i.e. to the left as shown in FIG. 7) so that the thrust springs 90 areimmediately compressed against the carrier blocks 101, which are held infixed positions on the shafts 28 by engagement of the balls 105 in thegrooves 89, since the balls 105 are held against outward displacement byengagement with the interior surface of the cylinders 91.

However, the groove 95 in each cylinder 91 is so disposed relative tothe shoulder 94 that when the shoulder 94 comes into engagement with thestationary carrier block 101, the groove 95 is then in alignment withthe transverse bores 103, 104 in the carrier block 101, thereby allowingballs 105 to move radially outwardly. Continued outward movement of thecylinder 91 can thus drive the carrier block 101 outwardly along theshaft 28, and displace the balls 105 radially outwardly into the grooves95 as shown in FIG. 6.

As outward movement of the cylinder 91 continues, the balls 105 are heldwithin the groove 95 by engagement with the exterior surface of theoutermost portion 87 of the shaft 28. At this time, the carrier block101 is held in a fixed position relative to the cylinder 91 (i.e.against the shoulder 94), by the detent action of the balls 105 in thegrooves 95, thereby holding the thrust springs 90 in a compressedcondition, as shown in FIG. 6.

As shown most clearly in FIGS. 7 and 8, the radial bores 103, 104 areeach of stepped form, with an internal shoulder 106 at the junctionbetween an inner portion 107, which is of such a diameter as toaccommodate the ball 105 with minimum clearance, and a somewhat widenedouter portion 108. The shoulder 106 of each bore is spaced from thesurface of the shaft 28 by a distance which is slightly less than theradius of the ball 105. The effect of this is that the shoulder 106assists in retaining the ball in the groove 95 while relieving thepressure exerted by the ball on the shaft 28. This facilitates movementof the carrier blocks 101 along the shafts 28 by reducing friction,since the balls 105 are pressed laterally against the shoulder 106 asshown in FIG. 9 in such a manner as to apply a radially outwardlydirected force to the ball, thereby holding it in the groove 95 while atthe same time relieving the pressure exerted by the ball on the shaft28.

In operation, the thrust springs 90 are initially in a relativelyunstressed condition as shown in FIG. 7 while the door is closed and arecompressed during the initial stages of the opening movement of the doorthrough a distance corresponding to movement of the shoulders 94 withinthe cylinders 90 into engagement with the carrier blocks 101 while thecarrier blocks are held in fixed positions on the shafts 28. The thrustsprings 90 are then held in that compressed condition, as shown in FIG.6, throughout the remainder of the movement while the carrier blocks 101are held in fixed positions in the cylinders 91 and travel with thecylinders, along the shafts 28.

When the door closes subsequently under the action of compressionsprings 45, the carrier blocks 101 are initially retained in their fixedpositions within the cylinders 91, since the balls 105 continue to beheld within the grooves 95 by the shaft 28 and the thrust springs 90 aremaintained in their stressed condition. But when the transverse bores103, 104 of the carrier blocks 101 again come into register with thegrooves 89 formed in the shafts 28, some way before the door reaches itsclosed position, at this point the balls 105 are free to move radiallyinwardly into the grooves 89, thereby moving out of the grooves 95formed in the cylinders 91, and releasing the cylinders relative to thecarrier blocks 101. The carrier blocks 101 are then held in a fixedposition relative to the shafts 28, and the thrust springs 90, acting onthe now fixed carrier blocks 101 exert an augmented driving force on thecross-head 35 over the final part of its range of movement as theshoulders 94 of the cylinders 91 move away from the carrier blocks 101as shown in FIG. 7.

The adjustment plate 12 enables the point at which the thrust springs 90come into operation to be varied. Adjustment of the adjustment plate 12relative to the mounting plate 11 of the anchor assembly 10 alters theangular position of the door at which the balls 105 become aligned withthe grooves 89 in the shafts 28 by varying the spacing between themounting plate 11 of the anchor assembly 10 and the cross-head 35 of theoperating member 30. In this way the fixed position of the grooves 98corresponds to any selected position of the mounting plate 11 within apredetermined range of positions. Typically, the range of adjustment maybe between 0 and about 15° of opening. Thus at one extreme, the thrustsprings may be rendered ineffective if desired, whilst the range ofangular movement over which they are effective, when required, can beset at up to 15° or thereabouts according to the precise geometryadopted.

This is illustrated in FIG. 10, in which the total force (F) exerted onthe operating member 30 is shown relative to the angle of opening (α).As can be seen from the maximum angle of opening (α_(max)) to anadjustable angle (α_(x)) the force is at an ideally constant value(F_(S1)). At the point (α_(x)) the force increases sharply to anaugmented value (F_(S2)) and ideally remains at that value throughoutthe remainder of the range of movement to the position of closurerepresented by (α₀). The angle (α_(x)) may be varied between zero (α₀)and typically about 15° as previously described.

In practice, the damper assembly 50 is, however, operative over theentire range of movement of the operating member 30 up to the “doorclosed” position to provide a controlled and adjustable rate of closureand thus a variable time to closure from any initial angle of opening aspreviously described, and the forces exerted by the closer are notconstant during each part of the closing movement as illustrated in FIG.10. Thus in a typical embodiment with the main springs 45 fullycompressed the closing force is initially 1040 Newtons (234 lbs.)whereas at approximately 16° opening angle and just prior to engagementof the thrust springs 92 the force is 612 Newtons (137 lbs.) whilst at14° when the thrust springs have come into operation the force isincreased to a total of 1308 Newtons (294 lbs.) of which 718 Newtonsarises from the thrust springs.

The effect of the damper is illustrated in FIG. 11 which shows the doorclosing speed (V) plotted against door closing time (T) from theposition of maximum opening to closure, with minimum and maximum dampingand an indication of the variable range of operation of the thrustsprings.

With the damping set at minimum, and the action of the thrust springsset at maximum, the door speed follows the upper solid line curve (M),from which it can be seen that at time= to the door accelerates fromrest to a uniform velocity V₁ and at time=t_(1a) the thrust springsbecome effective with the result that the door speed increases to ahigher velocity V₂ until at point A the door reaches its position ofclosure at time=t_(2a).

If the damping is set at the maximum value, the door speed follows thelower solid line curve (N) to a lower velocity V₃ and the thrust springsbecome effective at time=t_(1b) following which the door speed increasesto a value V₄ until at point B the door reaches its position of closureat time t=t_(2b).

However, if the thrust springs are rendered inoperative by appropriateadjustment of the plate 12, when the damping is set at minimum the doorcontinues to close at velocity V₁ as indicated by the broken line M′until at point A′ it reaches its position of closure at time t=t_(1c)whereas when the damping is set at maximum the door continues atvelocity V₃ as indicated by broken line N′ until at point B′ it reachesits position of closure at time=t_(2c).

The shaded area bounded by points A, A′, B and B′ represents theenvelope within which the closure time can be varied by the combinedadjustments available by means of the adjustment plate 11 and theadjustable throttle incorporated in the damper assembly 50.

Thus at all times during the closing action, the rate of movement of thedoor is controlled by the damper assembly 50 but, as illustrated in FIG.10, the closing force applied by the driving springs 45 can besubstantially augmented from F_(S1) to F_(S2) by the thrust springs 90over a variable final part (α=α_(x) to α₀) of the closure movement, thusovercoming any resistance to closure which may be imposed by a latchingmechanism operating between the door and door frame, but without thepotentially excessive “snap action” associated with previous doorclosures of the kind in which the flow restriction imposed by the damperassembly is relieved during the final part of the closure movement.However, adjustment of the damper makes it possible to provide acontrolled degree of snap action, when the flow restriction is set to aminimum, or a “soft” action, when die flow restriction is set to amaximum, or anything in between.

Adjustment of the position of the adjustment plate 12 of the anchorassembly 10 varies the effective length of the connection between thecross-head 35 and the anchor assembly, and can thus also enable theaction of the thrust springs 90 to cut in at the correct point despitevariations in the width of the gap between the inner edge of the doorand the door flame in different installations.

The door closer as above described is fully adjustable with respect tothe selected range of angular movement over which the augmented closureforce is applied, and with respect to the degree of damping applied,whilst being particularly compact so that it can be installed in a doorwithout compromising the fire resistance of the door.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately, or in any combination of such features, be utilised forrealising the invention in diverse forms thereof.

What is claimed is:
 1. A door closer comprising in combination: ananchor member (10) for mounting on a door frame, an actuator assembly(20) for mounting within the thickness of a door which is hinged formovement between open and closed positions relative to said door frame,an operating member (30) coupled by an articulated link (33) to saidanchor member (10) and mounted in said actuator assembly (20) for arange of movement between a retracted position in which said anchormember (10) is held immediately adjacent to said actuator assembly (30)and an extended position in which said anchor member (10) is held inspaced relation to said actuator assembly (30), resilient driving means(45) arranged to exert a driving force on said operating member (30) ina manner such as to drive said operating member towards said retractedposition and thereby draw said anchor member (10) and said actuatorassembly (20) together such that, when installed, the door closer actsto draw the door into its closed position relative to the frame, adamper (50) connected to said operating member so as to control the rateof movement of the operating member (30) in at least a direction towardssaid retracted position, said damper comprising a cylinder (52)containing hydraulic fluid, a piston rod (27) carrying a piston (51)which divides the cylinder (52) into two chambers (65, 66), andflow-restricting means (70-83) to limit the rate of flow of hydraulicfluid from one of said chambers to the other at least in one directionof fluid flow in response to movement of said operating member towardssaid retracted position, an adjustable throttle, which comprises twoelements (72, 82) in combination, the flow restriction imposed on thehydraulic fluid by said throttle being variable by relative positionaladjustment of said two throttle elements, and an adjustment member (80)to enable one of said throttle elements to be positionally adjustedrelative to the other so as to vary the flow restriction imposed on thehydraulic fluid by said throttle, resilient thrust means (85) arrangedto exert an increased driving force on said operating member (30),control means (100) whereby said thrust means (85) is operative to applysaid increased driving force to said operating member (30) over adefined part of said range of movement as said operating member (30)approaches said retracted position, corresponding to movement of thedoor over the final part of its movement into its closed position, andan adjustment member (12) operatively connected with said control means(100) to vary the point in the range of movement of said operatingmember at which said resilient thrust means (85) becomes operative toapply said increased driving force.
 2. A door closer according to claim1 wherein said control means (100) includes detent means (105) arrangedto hold said thrust means (85) in a stressed condition over the whole ofthe range of movement of the operating member (30) apart from saiddefined part of said range.
 3. A door closer according to claim 2wherein said thrust means (85) includes a compression spring (90)located within a guide member (91) which is coupled to said operatingmember (30) and slidable therewith along a fixed shaft (28), and saiddetent means (105) is provided on a carrier member (101) which isretained within said guide member (91) to abut one end of saidcompression spring (90) and is slidable on said fixed shaft (28) andlocated within said guide member (91) for limited movementlongitudinally thereof, the detent means (105) being engagable in aninternal recess (95) formed within said guide member (91) to hold thecompression spring (90) in a compressed condition, and beingdisplaceable from a position of engagement with said internal recess(95) to release said compression spring (90) at a predetermined positionalong said shaft (28) so as to apply said increased driving force tosaid operating member (30).
 4. A door closer according to claim 3wherein said detent means (105) is displaceable from said position ofengagement with said internal recess (95) in said guide member (91) intoa position of engagement with an external recess (89) formed in saidshaft (28) to hold said carrier member (101) in a predetermined positionon said shaft (28).
 5. A door closer according to claim 4 wherein saiddetent means comprises a plurality of balls (105) located in one or moretransverse bores (103, 104) formed in said carrier member (101).
 6. Adoor closer according to claim 5 wherein each of said balls (105) is ofa diameter greater than the radial spacing between an exterior face ofsaid shaft (28) and an interior face of said guide member (91) so thatsaid balls (105) are either held by said shaft (28) in said internalrecess (95) formed in said guide member (91) or by said guide member(91) in said external recess (89) formed in said shaft (28).
 7. A doorcloser according to claim 6 wherein the bores (103, 104) in which theballs (105) are located are formed with a radially innermost portion(107) having a diameter such as to accept the ball with a slightclearance and a radially outermost portion (108) having a greaterdiameter, the two portions meeting at an internal shoulder (106)disposed at a spacing from the shaft (28) which is less than the radiusof the ball (105).
 8. A door closer according to claim 7 wherein saidcylinder (52) of said damper (50) is moveable relative to said actuatorassembly (20) and is coupled to said operating member (30), and saidpiston (51) is static.
 9. A door closer according to claim 8 whereinsaid flow-restricting means (70-83) is incorporated into said piston(51) and piston rod (27), and said adjustment member (80) has anoperating element (83) which is accessible from one end of said pistonrod (27).
 10. A door closer according to claim 9 wherein said adjustmentmember (80) comprises a shaft located within an axial bore (75) formedin said piston rod (27), with an external threaded formation (81)engaging an internal threaded formation (77) in the bore of the pistonrod whereby rotation of the adjustment member (80) varies its axialposition within said bore (75).
 11. A door closer according to claim 10wherein said adjustment member (80) is provided at one end with a needleformation (82) which comprises one of said throttle elements toco-operate with an orifice (72) defined by the other of said elements,and at its other end with a head formation (83) whereby the adjustmentmember (80) may be rotated.
 12. A door closer according to claim 7wherein said thrust means (85) includes one or more spring elements (90)having a higher rate than said resilient driving means (45).
 13. A doorcloser according to claim 12 wherein both said driving means (45) andsaid thrust means (85) comprise one or more coiled compression springs(45, 90).
 14. A door closer according to claim 13 wherein said thrustmeans (85) and said driving means (45) each comprise two spring elements(45,45: 90,90) which extend in side by side parallel relationship anddisposed symmetrically relative to said damper means (50).
 15. A doorcloser according to claim 14 wherein said thrust means (85) are disposedbetween said driving means (45) and said damper means (50).